The Last Mile: Wireless Technologies for Broadband and Home Networks Carlos Cordeiro, H. Gossain, R. Ashok, & D. P. Agrawal OBR Research Center for Distributed and Mobile Computing University of Cincinnati – USA http://www.ececs.uc.edu/~cordeicm [email protected] 1 Course Overview and Outline • Main Goal – Investigate and understand the concepts and technologies needed in “The Last Mile” • Topics Covered – Introduction – Basics of Broadband Wireless Communications – Wireless Local Loops (WLLs) – Wireless Local Area Networks (WLANs) – Wireless Personal Area Networks (WPANs) – Conclusions and Future Directions 2 1 Wireless Technologies WAN (Wide Area Network) MAN (Metropolitan Area Network) LAN (Local Area Network) PAN (Personal Area Network) PAN LAN MAN WAN 802.11a,11b,11g 802.11 GSM, GPRS, Standards Bluetooth HiperLAN2 MMDS, LMDS CDMA, 2.5-3G Speed < 1Mbps 2 to 54+ Mbps 22+ Mbps 10 to 384Kbps Range Short Medium Medium-Long Long PDAs, Mobile Peer-to-Peer Enterprise Fixed, last mile Applications Phones, Cellular Device-to-Device networks access Access 3 Wireless Market Segments Wireless Market Segments & Partners Wireless Internetworking Overview Residential/ Fixed Mobile Premise/ Campus Broadband Multiservice 2G+ 3G IEEE BLUE Cellular Cellular 802.11 TOOTH Data Packet MMDS LMDS Services Data/Voice Cisco/ Bosch GPRS UMTS Mobile IP 4 2 Introduction Last Mile – Connectivity between local signal distributor (provider) and home (or the end user) – The interconnection and interoperation of • Home appliances • Entertainment devices • PC hardware • Networking devices • Security, lighting and environmental control systems Objective High-speed distribution of information (Audio, Video, and Data) requiring higher bandwidth 5 Why Wireless Broadband? • Provide the ability to access information and communicate anytime, anywhere – Bring the network to the hands of the consumer (Pervasive Computing) – Interconnect people in data, voice and video – Enables users to communicate and share data – Bring interconnectivity to intelligent devices – Portability and “no new-wires” 6 3 Envisioned Communication puzzle of 4G 4G provides a seamless integration of different types of wireless networks 7 Broadband Home Access (BHA) Architecture Four Components - Broadband Local Loop - Residential Gateway (RG) - Home Area Network (HAN) - Electrodomestic Network Devices (END) Residential Broadband Home Area Network Gateway (RG) Local Loop (HAN) Electrodomestic Network Device 8 (END) 4 • Broadband local loop – Connection between the local provider and consumer • Telephone Wires, Coaxial Cable, Fiber Optics, Wireless RF, Satellite Communications • Residential Gateway (RG) – Interface device connecting Broadband local loop and in-home network – Centralized access point • Home Area Network (HAN) – High speed network connecting ENDs, e.g., 10Base-T/Cat5 • Electro-domestic Network Devices (END) – Set of “intelligent” processing tools, e.g., computers, appliances and electronics 9 Review of Basic Concepts 10 5 dB (relative measure) $ 100B dB = 10 log (times) 1011 10,000 times 10,000 * 1,000 times = 10,000,000 times 40 dB Net worth 40 dB + 30 dB = 70dB 107 $ 10M 1,000 times 30 dB $ 10K 104 Bill Steve Grad 11 Path loss in dB 10 W P dB = 10 log (----)1 101 P2 Power Path loss from source to d2 = 70dB 10-3 1 mW 10,000 times 1,000 times 1 µW 10-6 40 dB 30 dB source d1 d2 12 6 dBm (absolute measure of power) 10 W = 40 dBm P dBm = 10 log (-------)1 101 1mW + 10,000 times Power 10-3 1 mW = 0 dBm - 1,000 times 1 µW = -30 dBm 10-6 source d1 d2 13 Radio Propagation: Path Loss (Free- space) Path Loss in Free-space 130 120 fc=150MHz 110 fc=200MHz fc=400MHz 100 fc=800MHz 90 fc=1000MHz Path Loss Lf (dB) Lf Loss Path 80 fc=1500MHz 70 0 5 10 15 20 25 30 Distance d (km) 14 7 Fading and Multipath Fading: rapid fluctuation of the amplitude of a radio signal over a short period of time or travel distance Tx Rx Effects of multipath • Fading • Varying doppler shifts on different multipath signals • Time dispersion (causing inter symbol interference) 15 Bandwidth of Digital Data Fourier transform Time domain Frequency domain Signal amplitude 0.5 Mhz 1 Mhz 1.5 Mhz baseband signal (1 Mbps) • Baseband signal cannot directly be transmitted on the wireless medium • Need to translate the baseband signal to a new frequency so that it can be transmitted easily and accurately over a communication channel 16 8 Channel Coding and Modulation low Q high Q modulation demodulation channel coding channel decoding baseband signal baseband signal 17 Last Mile Broadband Wireless Access 18 9 Last Mile Broadband Wireless Access Several wireless systems in several bands competing for “last mile” Infrared (IR) - Line of Sight (LOS) - Diffused-IR can work without LOS Radio Frequency (RF) - Narrow Band → microwave - Spread Spectrum → FHSS, DSSS Interconnect class of devices which constitute a sub- network with wireless technology 19 Services and Carrier Requirement of BWA • Internet Access, Multiline voice, Audio, Streaming video • Quality of Service (QoS) guarantees • Scalability • Radio Interoperability 20 10 Deployment Scenarios for BWA Supercell • Supercells Macrocell – Cell radius ~ 30mi – Single-cell Configuration Microcell • Macrocells – Cell radius ~ 5mi Picocell ??? – Frequency reuse between cells • Microcells – Cell radius ~ 1mi – Provides indoor coverage 21 Challenges in Fixed Wireless Networks • Technology Standardization • Higher Data Rate • Sophisticated physical and radio link layers – To maintain reuse factor of 3 F7 F2 • Reliability F7 F2 F6 F1 F3 F6 F1 F3 F5 F4 F7 F2 F5 F4 F7 F2 F6 F1 F3 F6 F1 F3 R F5 F4 eu se d i st F5 F4 an ce D 22 11 BWA Channels Wireless channel are limited by radio spectrum availability, path loss, interference and multipath propagation Building •Multipath •Delay Spread •Path Loss •Fading (Fast and Slow) Direct Signal Reflected Signal hb Diffracted Signal hm d Transmitter Receiver 23 BWA system: Physical Layer Modulation 1. Single-Carrier (SC) Modulation with Equalization (several equalization options) • Maximum-likelihood (ML) Equalization – Computationally Complex • Decision-feedback Equalization (DFE) • Linear Equalization High Delay and/or high data rate requirements pose limits on the performance of SC systems 24 12 Physical Layer (cont.) 2. Direct Sequence Code-Division Multiple Access (DS- CDMA) • Spreading code sequence at higher data rate is used to spread the transmitted symbol in frequency. – The larger the spreading factor (SF), the larger the operating bandwidth has to be » 160 MHz for a SF of 32 » 3G = 4 MHz for a SF of 4 • RAKE receiver can be used for frequency diversity. 3. Orthogonal Frequency-Division Multiplexing (OFDM) • Uses guard interval (cyclic prefix) which changes with delay spread and/or data rate. • Transmitter : Inverse Fast Fourier Transform (IFFT) • Receiver : Fast Fourier Transform (FFT) 25 Physical Layer (cont.) 4. Ultra-Wideband Modulation (UWBM) • Sub-nanosecond pulses are used to convey information • Pulses are transmitted across an ultra-wideband spectrum, and appears as a noise to other systems. Some Issues – Hardware Considerations • OFDM is less complex than SC and DS-CDMA, but it makes the system sensitive to power amplifier nonlinearities. – Channel Coding (e.g., amplitude, phase) 26 13 Physical Layer (cont.) – Synchronization • OFDM is more sensitive to synchronization errors than SC and DS-CDMA – Link Adaptation • Dynamic variation in modulation and FEC can be used for better channel throughput. – Multiple Access • Time Division Multiple Access (TDMA) • Code Division Multiple Access (CDMA) – Time Division Duplex (TDD) vs Frequency Division Duplex (FDD) 27 MAC Layer and Radio Link Protocol (RLP) MAC Functions – Scheduling • Uplink and downlink transmission • Support multiple service flows – Admission Control • Enforce Policy and Authorization • Accommodate QoS requirement of new flow 28 14 MAC Layer and RLP (cont.) – Link Initialization and maintenance • Channel Choice, Synchronization, Registration, and Security Issues – Support for Integrated Voice and Data • Bandwidth guarantees, bounded loss, delay and jitter – Fragmentation, Automatic Repeat Request (ARQ), Adaptive Modulation and Coding 29 MAC Layer and RLP (cont.) MAC Features – Fragmentation – Retransmission – Scheduling Support – Link Maintenance and Support 30 15 Multiple Antennas in BWA Multiple antennas to provide high-data-rate and high-quality wireless broadband access Features – Array gain • Combine signals to increase C/N (Carrier-to-noise) ratio – Diversity gain • Spatial diversity – Interference suppression • Suppress CCI (Co-Channel Interference) – Multiplexing gain • Open up parallel spatial data pipes within the same bandwidth 31 Last Mile Broadband Wireless Access Technologies 32 16 Last Mile Broadband Wireless Access Technologies • Multichannel Multipoint Distribution System (MMDS) • Local Multipoint Distribution Service (LMDS) • Satellite Communications • IEEE Standard 802.16 • IEEE 802.11 as a Last Mile Alternative • Various Standards 33 Multichannel Multipoint Distribution System (MMDS) • Analog-Based • Initially – Two channels • Later – Thirty-one 6 MHz channels in 2.5 to 2.7 GHz frequency band • In 1983, FCC allocated 200 MHz bandwidth for licensed network 34 17 MMDS Components Antenna and MMDS tower downconvertor Central head- end 2.1 and 2.7 GHz Telephone Network Antenna and downconvertor MMDS tower MMDS Broadband Connectivity 35 Local Multipoint Distribution Service (LMDS) • Architecture similar to MMDS • Base Station to end user → Point-to-Multipoint